Q: When and how much can I prune my overgrown hydrangeas? — J.O., Houston

A: The traditional spring-flowering Hydrangea macrophylla, the mophead hydrangea, blooms on old wood, so it's best to prune after the spring blooms. The shrub will set buds later in the summer. If you prune in the fall, you're likely to remove those buds and the following spring's flowers. It is OK to prune them back a third after that spring bloom. These hydrangeas can look straggly, even dead in winter, and we're tempted to prune. But doing so removes blooms.